Analysis of phase-angle histograms from equilibrium radionuclide studies: Correlation with semiquantitative grading of wall motion

Abstract

Quantitative wall motion assessment from gated radionuclide left ventriculograms using phase analysis was studied in 14 subjects (6 normal volunteers and 8 patients with previous acute myocardial infarction). The standard deviation and skewness of the phase-angle histograms were determined from both global and segmental left ventricular (LV) regions of interest (septal, apical and posterolateral). Studies were performed at rest, after administration of atropine and after combined administration of phenylephrine and atropine. Both the standard deviation and skewness showed significant correlations with semiquantitative wall motion scoring. From the global analyses, the highest correlations were found after atropine administration (r = 0.86, p < 0.001 for standard deviation and r = 0.72, p < 0.001 for skewness). Nevertheless, deterioration in global wall motion scores correlated poorly with directional changes in standard deviation (r = 0.06, difference not significant) or skewness (r = 0.33, p < 0.05). No significant correlation between skewness or change in skewness and wall motion scores were found with the segmental analyses. The maximal correlation between segmental standard deviation and segmental wall motion grading was again noted after atropine administration (r = 0.68, p < 0.001), but deterioration in grading did not correlate with similar deterioration of the standard deviation (r = −0.05, difference not significant). Based on 90% confidence limits for normal standard deviation and skewness, an abnormal standard deviation (>14.5) identified 13 of 28 wall motion disorders (sensitivity 46%), whereas an abnormal skewness (>1.4) identified 1 of 28 wall motion disorders (sensitivity 4%). In conclusion, the presently implemented methods of phase-angle analysis in clinical use are insensitive in characterizing wall motion disorders. This limitation is most profound in the assessment of directional changes in wall motion.